1. Field of the Invention
The present invention concerns nuclear power, the operation of sodium-cooled fast-neutron reactors and, more precisely, relates to the field of valves. The present invention advantageously relates to valves for the circulation of liquid metal, such as liquid sodium, heated to a high temperature which may, for instance, reach 450° C.
2. Description of the Related Art
Fourth generation cooled reactors such as the ASTRID (Advanced Sodium Technological Reactor for Industrial Demonstration) reactor use a liquid metal, generally sodium as a coolant. Such coolant, in addition to having a very high temperature, typically above 400° C., is generally chemically very reactive.
It is thus essential to provide as reliable tightness as possible all along the travel of the fluid and more particularly at the valves.
To control the sodium flow, several valve types have been developed. Such sodium valves use a shutter so configured as to cooperate with a seat so as to prevent the liquid sodium from flowing. A control device has a motorized or manual wheel, connected by a mobile rod to the shutter and the actuation of which makes it possible to selectively move the shutter closer to, or away from the seat.
To provide tightness, a first type of sodium valve uses a solidified sodium gasket. In such type of sodium valve, a portion of the valve in contact with the mobile rod is so configured as to receive the liquid sodium and lower the temperature thereof. In this portion, the sodium solidifies and provides tightness to the outside. Other tight members such as gaskets are also used.
The specific drawback of such valve type is that it requires a complex system for holding the actuating device and the tightness system. As a matter of fact, the actuating device and the tightness system form an important mass. Besides, such important mass is relatively offset relative to the duct which increases the risks of breakage, more particularly in case of an earthquake. To reduce the risks of breakage, complexes and expensive holding systems are thus used, today.
A second type of sodium valve provides tightness by bellows. In such sodium valve type, the rod is equipped with bellows forming a barrier for the passage of the liquid sodium.
Such valve makes it possible to somehow reduce the offset between the duct and the actuation and tightness device although such offset is not totally eliminated. On the other hand, such valve type implies many mechanical parts, which will wear and reliability is thus limited.
A need therefore exists, which consists in providing a valve making it possible to reduce or even eliminate at least one of the drawbacks entailed in the known valves for liquid sodium.
The present invention aims at meeting such need. More precisely, the present invention aims at reducing the complexity of the systems holding the control and tightness devices of the existing sodium valves and/or improving the reliability of the tightness thereof.